The origin of "Raku" ware, which is now known worldwide as a ceramic technique, was founded by Raku Chojiro during the Momoyama Period of 16th century Japan. This unique ceramic tradition has been conveyed through fifteen generations of Raku potters to the present. The term Raku comes from "Rakuyaki", and the two are used interchangeably. Rakuyaki in turn originated from "Jurakudai", a representative architectural design during this period. The origination of the term also meant the birth of the Raku family name, started by Chojiro, the founder. Later, Raku designated Japanese families given permission to use the character "Raku" to identify their ware. Raku loosely translates to enjoyment or pleasure.
The traditional Raku tea cup was used in addition to the Zen tea ceremony. Being uneven and simple in shape, and having the accidental surface effects from the fire, the cup was valued as much for how they felt in the hand as their appearance when filled with the frothy green tea.
Raku is made in many styles but, because of the thermal shock to which it is subjected during final firing, the typical piece has been fairly small. Pieces are usually sturdy hand built forms and often asymmetric with seamless joints.
Today, Rakuyaki has spread worldwide as a field of ceramics. However, back in Momoyama Period, the term only referred to the earthenware made by the Raku family. The present Kichizaemon Raku is the fifteenth generation since Chojiro. Raku is now used in the west, however the word refers to a variety of techniques greatly modified from traditional methods, such as ready made Raku kilns, bright colors, low-fire glazes, and various chemical additives and compounds In addition, nontraditional Raku usually involves various methods of reduction and post firing fuming (or smoking).
When forming the piece, the body must be open and grogged but need not be coarse textured. Any clay can be used as a Raku body, but it is important to use clay that is formulated to withstand the quick heating and cooling of the Raku process. Most clays will require the addition of approximately forty percent of an opening material, as a coarse clay tends to crack less.
When one is using the Raku technique it is good to keep in mind while building their piece that the ware has many dangerous steps it must endure. A piece that is too thin, or fragile with handles or delicate attachments is quite susceptible to breakage. The ware is subjected to extreme shock entering and exiting the red hot kiln, so pinching and carving, the traditional way, is ideal.
A Raku piece may be made on the wheel, but if it is hand built the seams must be properly scored and tightly joined.
As with all ceramic work the type of clay that is used will contribute to the outcome of the piece. In Raku a red clay will give a soft pink blush through semitransparent white glazes. China or ball clay can be added to improve the quality of the pink. To give brighter colors to under-glaze and colored glazes a white clay can be used. Porcelain, which is a much higher fire than Raku will give, makes a porous surface on the ware. With the surface being highly porous, more carbon is able to be absorbed in the post-firing reduction and smoking, thus causing a smooth black on the unglazed portions of the ware.
Using a Raku kiln is seen as experimental involvement with heat and ceramics. Raku is described in The Potters Dictionary of Materials and Techniques as, "A state of mind rather than a technique. The Zen philosophy of self discovery through contemplation, of allowing accidents to happen, is respected."
The kiln is often a temporary structure built outdoors and fired by charcoal, coke, wood, oil or gas. There are many different variations of kilns, though not usually as unique as Rachael Porter's Bug. The ware should first be bisque fired to the recommended temperature for the clay you are using- generally from r 015 (1479 °F/ 840 °C) to r 05 (1915 °F/ 1046 °C).
I was fortunate enough to be present during a Raku firing at Glen Echo Pottery. The firing was instructed and coordinated by Jeff Kirk. There were multiple firings being done that night. Jeff informed us that the pieces were loosely packed to allow for expansion "The initial firing would take forty minutes or so, and each subsequent firing would dwindle down to seven or eight minutes." The time frames are not precise as they are determined by many factors such as outside temperature, size of the pieces and kiln fuel. The decrease of the firing time throughout the process is due to the accumulated heat in the kiln. A kiln check was made about twenty minutes into the first firing. Due to the variation in time and temperature for each load, the kiln was checked often for progress. Jeff said, "If the glaze looks molasses-ie with bubbles it is not ready." As the night air was cooling, and the kiln was retaining more heat. A few students were instructed to pre-warm the wares in an electric kiln to reduce the thermal shock of entering the kiln.
When the glaze became shiny and fluid, and the ware was red hot, they were then removed and placed in various types of reduction chamber. The Glen Echo Pottery students had some metal trash cans and some brick chambers to choose from. The metal trash cans seemed to be the safest bet to me, as the combustible had sudden flare ups when ignited by the ware, and the trash can provided a higher wall, with a larger lid to shield the student. Combustibles can be almost any organic substance, such as: sawdust, peat moss, leaves, hay, straw, pine needles, wood chips, and news paper. I read a technique some where that I will test next summer. When the pot is red hot it is removed from the kiln and set on a thin layer of pine needles. A handful of needles is quickly placed on the shoulder. Then the piece and needles are quickly covered with a metal bucket. Earth is packed around the lid of the bucket (which is flush with the ground). The earth seals the smoke in, and will help keep the carbon in the reduction atmosphere, resulting in almost smokeless firing. Allow about fifteen minutes or more, to smoke and cool a bit before removing the bucket.
When the ware is removed from the chamber it is usualy still quite hot, so both care and tongs should be used. The ware may be sooty and ashy when removed. Some potters leave the soot on the ware for aesthetic reasons, otherwise the pot may be scrubbed with scouring powder and a brush. If the warm piece is dunked in cool water or sprayed with a spray bottle, the glaze forms a crackle effect.
Email the Artiste